Evolution of chromium and cobalt serum levels after the use of a modular neck stem in primary total hip arthroplasty. / Evolución de los niveles séricos de cromo y cobalto tras el empleo de un vástago con cuello modular en la artroplastia total de cadera primaria.

ABSTRACT

INTRODUCTION AND OBJECTIVES: Modular neck primary stems were introduced with the theoretical advantage of restoring the hip anatomy more precisely. However, the presence of a second junction has been associated with increased corrosion and release of metal debris. The objective of our study is to quantify of chromium and cobalt serum values, and to analyze their temporal evolution during five years. MATERIAL AND METHODS: We present a prospective series of 61 patients who underwent primary total hip arthroplasty by implantation of the HMAX-M® stem (Limacorporate, San Daniele, Italy). Serum chromium and cobalt determinations were performed at six months, two years and five years. RESULTS: Our series shows a progressive elevation in chromium levels with a significant difference between chromium values at six months (0.35±0.18) and five years (0.52±0.36), P=.01. Regarding cobalt, a statistically significant elevation is observed between six months and two years and a subsequent stabilization of values between two and five years, with a cobalt mean at six months (1.17±0.8) significantly lower than at two (2.63±1.76) and five years (2.84±2.1), P=.001. CONCLUSION: Elevated serum cobalt levels have been observed in patients who underwent modular neck stem implantation. The results obtained in this study have limited the use of stems with a modular neck in our clinical practice.